A slit system used as a collector slit in a magnetic-sector mass spectrometer is required to adjust the slit width at an accuracy on the order of micrometers (microns). A slit system of this kind which has been heretofore used in a magnetic-sector mass spectrometer is designed, for example, to use a differential gear, drive mechanism. The drive mechanism accurately moves a pair of slit blades. The slit is adjusted either by manually rotating a driving shaft or by a stepping motor coupled to the driving shaft. Thus, the slit width is adjusted.
Another known slit system employs bimorph piezoelectric devices. (A bimorph piezoelectric cell comprises two piezoelectric plates cemented together in such a way that an applied voltage causes one to expand and the other to contract.) Blades forming a slit are mounted to the front ends of these piezoelectric devices. The blades are directly moved to adjust the slit width.
The slit system using the differential gear is bulky and thus a small-sized mass spectrometer does not have sufficient space to accommodate such a large slit system. Furthermore, this system is complex in structure and made up of a large number of components. Hence, this system is expensive.
The slit system using the bimorph piezoelectric devices does not permit the slit to move a great distance. Therefore, it is difficult to control the slit over a wide range.